Cellulosic textiles reacted with aldehydes in an azeotropic medium



Patented May 25, 1954 UNITED S'i'i Ii i:-.-

OFFICE CELLULOSIC TEXTILES REACTED WITH ALDEHYDES IN AN AZEOTROPIC ME- DIUM Joseph W. Schappel, Morton, Pa, assignor to American Viscose Corporation, Wilmington, DeL, a corporation of Delaware 11 Claims. 01. 8-116.4)

This invention relates to the treatment of hydroxylated textile materials such as regenerated cellulose with aldehydes which react with the hydroxyl groups of the textile to form acetaltype bridges between the hydroxyl groups. The invention is of particular advantage in the modification of textiles composed of or comprising regenerated cellulose with formaldehyde and will be described more in detail in connection with that embodiment. This is a continuation of my application Serial No. 65,741, filed December 16, 1948, now abandoned.

The term textile material includes filaments, fibers, staple or yarns, whether in the finished condition or at some intermediate stage in their production, as well as fabrics, such as knitted, woven or felted fabrics, and garment or other articles made from them.

It has been proposed heretofore to react textile materials with aldehydes, and especially formaldehyde, for increasing the strength, especially the Wet strength, of the textile, or to improve its resilience, crease resistance, and/or resistance to shrinkage, and to reduce the extent to which the materials are swollen by water. However, in spite of the fact that formaldehyde is known to improve various properties of the textile, the formaldehyde treatment has not been used commercially except in a few isolated instances, apparently because of the difliculty of insuring uniform reaction of the hydroxyls of the textile with the formaldehyde and of obtaining predictable, reproducible results.

The uniformity of the aldehyde-modified textile is determined by the number and distribution of the acetal bridges between the hydroxyl groups of the textile, which in turn depends on the extent to which the textile is swollen during the reaction of the hydroxyls and the aldehyde, and the uniformity of distribution of the aldehyde on the textile when the latter is heated to bring about the chemical reaction resulting in the formation of the acetal bridges.

The method generally proposed in the prior art for modifying regenerated cellulose textiles or the like with formaldehyde has involved treating the textile with an aqueous medium containing the formaldehyde and an acid catalyst, drying the impregnated textile, and finally heating it to baking temperature to complete the chemical rein an inert liquid heated to the elevated temperature required to complete the chemical reaction. It is impossible to produce a uniformly formalized textile or to duplicate results from batch to batch by these procedures because of variables which cannot be controlled.

When the textile impregnated with the aqueous treating liquid is dried before it is heated to the elevated temperature at which the chemical reaction is completed, it shrinks progressively as the amount of water present in or on the yarns is reduced. some acetal bridges are formed during the drying, and since the textile changes from a more highly swollen condition to a less highly swollen condition as the drying proceeds, those acetal bridges formed during the drying are formed while the textile is swollen to an extent which is different from one end of the drying period to th other, and also different from the extent to which the textile is swollen when it is heated to the elevated temperature for completing the reaction. As a consequence, and since uniformity of cross-linking in the treated textile depends on uniformity of swelling of the textile when the cross-links (acetal bridges) are formed, a uniformly modified textile in which the acetal bridges are uniformly distributed along the cellulose chains is not obtained.

A further difficulty encountered with those prior art method is that when th impregnated textile is dried or partially dried between the impregnation with the aqueous treating solution and heating or baking thereof at the elevated temperature, some of the formaldehyde present in or on the impregnated textile is lost by evaporation. The amount of formaldehyde carried by the dried fabric is less than the amount applied to it by treatment with the aqueous treating solution, and as the amount lost by evaporation may vary from batch to batch, and, moreover, is not uniform at all portions of the textile in any batch, it is difiicult to control the amount of formaldehyde carried by the textile when it is heated to complete the reaction and insolubilize the formaldehyde in situ on the textile. These difiiculties exist whether the chemical reaction is brought about by subjecting the impregnated, dried textile to dry heat or by heating it while it is immersed in an inert liquid. Even when the impregnated textile is not dried before it is immersed in a heated inert liquid for completing the chemical reaction, the results are not reproducible under the conditions which have been heretofore su gested for effecting the reaction.

The primary object of this invention is to nrnvide a process for modifying hydroxylated textile materials, specifically regenerated cellulose textile material, with an aldehyde, such as formaldehyde, whereby auniformly modified textile is ob-- tained and the results are always reproducible. A further object is to provide a process in which all of the acetal bridges formed by reaction be tween the hydroxyls of a regenerated cellulose textile and the aldehyde are :formedjzwhilea the" textile is in a uniformly swollen'condition. Other objects of the invention will appear hereinafter.

The objects of this invention are-sachievedxby immersing a dry or substantially dry textileconr prising yarns or fibers of a hydrophilic hydroxy 4 containing fiber-forming material, .such as. a re.- generated cellulose textile containingat most its normal moisture of regain, irr-a liquidbathcomprising water, a cross-linking agent, an acid catalyst, and a water-miscible liquid which is not itself a swelling agent fort the textile material or reactive with the aldehyde at'acid pH, which bath is" preheated to the temperature at. which the chemical reaction between the hydroxyls of: the textilematerial and :the aldehyde istotake. place but-- below its boilingrpoint under the pressure conditions prevailing duringithe reaction; whereby thetextile isrimpregnatedwwith the bath and the reaction betweenthe textile. andxthei aldehyde completed between the time the textile is immersed in the bath audits. removal from the bath,.a substantial reactionuproduct of the te"- tile material and crosselinkingagent being formed in .situinlthe fibers of .the .textilematerial. The aldehyde cross-linking agents of thepresent in ventioniwhich react chemically-with the hydroxyls of the textile are. formaldehyde, glyoxal, and pyruVicLaldehyde.

The textile to be modified iszhydrophilic and readily. swollen by the water present. in the bath;

In ordertto provide a fiexible,apredictabl process adaptedito the production of textiles theproperties ofwhich aremodified tothe desired extent, which can be predetermined; it: is importantfto regulate the extentto-which'theitextile is swollen during. the reaction between the hydroxyls and the cross-linking agent.

In the'present method; .the' swelling effect. of the water on the textile'iis-regulatedby thenonswelling. agent present with the waterin the bath, the-extent to which-the textile is swollen being controlled by the relative proportions of the water and non-swelling agent.

Examples of the non-swelling agents,- which must be water miscible but which -must be free from anyjsubstantialswelling effect onzthe textile and must not reactwith the aldehyde at acid pH- include water-miscible ethers such as diethylen glycol diethyl ether; dimethoxy, tetraethylene glycol, and 1,4-dioxane, and water-miscible ketones such as acetonyl acetone. Theseparticular water-miscible ethers and ketones are generally characterized by. thefactthat they form azeotropes withwaterhavinga boiling point of at least 80 C., specifically in .therange of 80 to 110? C., do notswelllthe. celluloseor other. hydrophilic textile, have an affinity or attraction for water. which is greaterthanthat ofcellulose, and function, in the presentprocess, to. control the extent to which the textile is swollen .by the water used inmaking upthesbathor. split. off in the reaction of the hydroxyls and the. aldehyde.

The. concentration of the water-miscible non swellingagent in'the treating. -,bath.may be between 70 and 95%ubYjV01llHlB,,bfiSSdiOll the total volume: of the-bath.- The amountofi aldehyde present in the bath varies inversely with the amount of non-swelling agent between 10 and 2.5%. Generally, the amount of fixed formaldehyde required to modify the properties'of regeneraued cellulos is in the range of 0L5 to 2% on the weight of the textile.

In one preferred embodiment of the invention the liquid treatingbath or solution has the following composition: from to by volume of 'non-swellingagent, from 7.2 to 3.6% by weight of aldehyde (20 to 10% by volume of 36-38% formalin), from 0.01" to 1.5% by weight of the acid reecting catalyst, and the balance water. Any water-soluble acid or acid-liberating salt which catalyzesthe reaction between cellulose and 'formaldehydeozan be used.

The-textileis-entered into the treating bath at a temperature below the boiling point of the treatingsolution, preferably about 2 0. below the boiling point, under the existing pressure conditions and thetemperature of the: bathzis-rrraintained constant throughout the treatment sothat: the temperature is uniform at all portions of: the textile: duringcthe entire process. This. is y in marked contrast tothe variations in temperature at different portions. of the textile which: occur when. it. is impregnatedzwith the treating-bathin'one' stage. and then transferred to another stage for heating" towurerthe aldehyde. The fabric or other textil may be preheatedto. the temperature of the bath before'itis enteredin the heated bath if desired.

By controlling; the relative proportions of the waterand water-miscible non-swellingagent and the proportion of aldehyde. in thebath; the extent ofswelling of the textile andthe number-of acctal bridges-introduced are. predetermined and controlled. The results can be'reliabl-yreproducedfor textile material ofi a given-kind by; preselectlon of these conditionswithinthe broad and specific ranges indicated.

By the present method, in which the regenerated cellulose or-the like is reacted with the aldehyde-while'it is in a condition of uniform swelling controlled by the proportion of water to water.-

miscible, non-swelling agent throughout-both the impregnating and curing stages, the acetal bridges-formed are all formed while the cellulose isiswollen to the same. extent: Therefore; the acetal bridgesare distributed through the cel-- lulose uniformly or substantially uniformly, and the textile is uniformly modified. The desired modifications of the textile, such .as-the decrease in the water retentioncapacity andstabilization of the textileagainst. progressive dimensional shrinkage on repeated laundering, improvement in crease resistance, etc. can be and are obtained without prohibitive loss of other good properties such as tensile strengthand elongation and, in the caseof discontinuousfibers, without loss of cardability of the fibers.-

The following examples, in Whichthenone swelling agent is by volume and the aldehyde and catalyst are by:weight,.illustrate specific embodiments. of the invention.

EXAMPLE I inthetable. The staplewas held in the preheated.

The. baths werepreheated.

solution for the periods of time shown in the table, removed from the bath, flushed with cold water, and washed for 5 minutes in a 1% NazSOa solution to remove excess unreacted formaldehyde. It was then rinsed in water, given a soft finish by treatment with a dilute aqueous medium containing sorbitol monopalmitate, and dried at 85 C. Results of the treatments are summarized in Table I.

The water retention denotes the amount of Water retained by a textile material after it is thoroughly wet out and centrifuged under specified conditions. test are held constant, the percent water retention is a direct indication of the extent to which the fiber swells in water. It corresponds to the results obtained by the microscope technique according to which the cross-sections of the fibers are photographed dry and wet and the area is measured by the planimeter. Thus, in Example I, the conditions for all of the tests were the same and the percent water retention for the treated samples (A to D, inclusive) as compared to that for the control, is a measurement of the extent to which the textile material was modified by the treatment.

The modified staple fibers were spun into a 30/1 yarn and woven into fabrics having the construction 72 warp x 64 filling. The greige fabrics were then: (1) desized by washing, dried relaxed, and measured for shrinkage; (2) subjected to the CCC-T-191 treatment described in Federal Standards Stock Catalog, Section 4, Part 5 (Supplement to Federal Specifications for Textiles), dried relaxed, and measured for shrinkage; and (3) again thoroughly wet out and washed in warm water, whizzed to remove excess moisture, ironed on a fiat bed press, and again measured for shrinkage. These fabrics were compared with a greige fabric woven from untreated regenerated cellulose staple which Was wet out, dried, and measured for shrinkage in the same manner as the fabric woven from the formalized staple. The results of these treatments (1), (2) and (3) are shown in Table II below:

As long as the conditions of the progressive dimensional shrinkage on repeated laundering, -or for any other modification of the fabric, the treatment may be performed on the fibers, yarns, or on the fabric as such.

. Regenerated cellulose textile materials treated in accordance with the present invention are no longer soluble in cuprammonium solution.

EXAMPLE II An aqueous solution containing 3.6% of formaldehyde, 0.3% of hydrochloric acid and of acetonyl acetone was preheated to 84 C. Skeins of 150 denier, 30 filament, 3 turns per in. twist viscose rayon yarn were immersed in the solution for 5 minutes at 84 C., withdrawn, washed with cold water, soaked for 5 minutes in a 1% NaaSOa solution, rinsed with water, given a soft finish, and dried at 85 C. The yarns were impregnated with the solution and the formaldehyde was reacted with the regenerated cellulose while they were immersed in the solution.

PROPERTIES Percent Strength 'lcnsile g1/den1er Retention Dly Wet 1 Control l as 2.3 1.2 Treated 44 2. 1 1. 2

EXAMPLE III An aqueous solution containing 4.8% of formaldehyde, 88% of l',4-dioxane, and 0.021% hydrochloric acid was heated to C. Skeins of 300 denier, 80 filament, 3 turns per inch twist viscose rayon yarn were immersed in the solution for 3 minutes at 100 C., withdrawn, washed with cold, then hot, water, soaked for 5 minutes in 1% NazSOs solution, rinsed in water, and dried.

An aqueous solution containing 4.7% of formaldehyde, 0.021% of hydrochloric acid, and 87% of dimethoxytetraethylene glycol was heated to 81 C. Skeins of 300 denier, 80 filament, 3 turns per inch twist viscose rayon yarn were immersed in the bath for 10 minutes at 81 C. The yarn was then withdrawn and after-treated as in Ex- Table II ample I.

( 60 PROPERTIES Warp Fill Warp Fill Warp Fill Tensile Strength,

Percent g./d.

2 16. s 9. 3 1s. 5 12. 1 14. 1 s. 4 Retention 11.4 4.1 13.9 7.6 11.0 6.1 D w n 9.2 3.1 11.6 6.2 9.1 4.6 W e 8.9 2.4 11.1 4.8 8.9 2.7 9.6 1. 3 12.1 3. 7 8. 8 2. 4 Control 85.0 2. 3 1. 2 Treated 47. 8 2. 0 1. 0

As will be obvious, the fabrics woven from yarns spun from the formalized staple fibers are characterized by increased resistance to progressive dimensional shrinkage on repeated laundering as compared to fabrics made from yarns of the untreated staple fibers. For this purpose of stabilizing regenerated cellulose fabrics against In all cases it was found that the cross-sectional swelling of the regenerated cellulose fibers on exposure to moisture was reduced, and this reduction was not accompanied by prohibitive deterioration of the other properties of the fibers, such as tensile strength, extensibility, etc. The

cardabilityi of staple fibers treated: in accordance with the invention was satisfactory.

EXAMPLE V .Anaoueous solution containing 35% of diox- .-ane,.4%. glyoxal, and about 0.03% of hydrochloric PROPERTIES Tensile, gJd.

Percent H2O Retention Dry "Wet The invention is particularly advantageous when the hydroxylated textile material to be modified is regenerated cellulose. However, other textile materials containing available hydroxyl groups can be modified uniformly by the treatment, including cotton, low-substituted (substitution less than 1) cellulose ethers which are hy- ..drophilic and water-swellable but insoluble in water, and cellulose esters which are hydrophilic and water-swellable, but insoluble in water.-

Such cellulose esters and ethers as may be soluble inthe lretones 01716131718175 used in the treating .bath are excluded.

The Water-miscible, non-swelling agent forthe textile predominates in the treating liquid for the i textile.

'Theoutstandmg advantages of the invention are: (a) the extent to which the textile is modified can be predetermined; (b) theconditions can be easily controlled for predetermined results; (c) the results can be reliably reproduced from lot to lot.

Some changes and modifications can be made in the above described details without departing from the nature and spirit of the present invention, and it is to be understood that the invention is not to be limited except as defined by the appended claims.

I claim:

1. A method comprising the step of introducing a hydrophilic, water-swellable, water-insoluble cellulosic textilematerial containing'free hydroxyl groups in the molecule into-a heated reaction inedi in which exerts a controlled swelling action onthe textile and-contains water, between 2.5% and by weight of an aldehyde selected from the groupconsisting'of formaldehyde, glyoxal, and pyruvic aldehyde, from 0.01 to 1.5% by weight of an acid-reacting catalyst, and between '70 and 95% by volume of a water miscible liquid which is free from any substantial swelling effect on the textile and does not react with the aldehyde under acid conditions, said water-miscible liquid having an afiinity for water greater than that of cellulose and forming an azeotrope with water boiling in the range of 80 to 110 (3., the temperature of said medium being 8 maintained substantially constant from the. time of introduction throughout 1 the reaction .at .a point raised sufiicientlytoefiect reactionbetween the textile material and the aldehyde but. below theboiling point of the medium underthe pressure prevailing .during. the reaction.

2. The-method .of claim-1, wherein the aqueous medium is preheated to and maintained during the reaction at a temperature about 2 C..below its boiling point.

3. The method of claim 1, wherein the water- .miscible liquid is an ether.

4. The method of claim 1, wherein the watermiscible liquid is a .ketone.

5. The method or claim 1, wherein the textile material is of regenerated cellulose and the al- .dehyde is formaldehyde.

6. The method of claim 5, wherein the watermiscible liquid is 1,4-dioxane.

'7. The method of claim 5, wherein the watermiscible liquid is acetonyl acetone.

8. Themethod. of claim. 5, wherein the watermiscible liquid is. diethylene glycol diethyl. ether.

9.1The. method. of claim 5, wherein the watermiscible. liquid 15. dimethoxy tetraethylene glycol.

10.. A method comprising the step of introducing .a hydrophilic, water-swellable, water-insoluble .cellulosic textile material containing tree hydroxyl groups in the molecule into a heated reaction medium .which exerts a controlled swelling action on the textile and contains water, between 2.5% and/10% by weightof an aldehyde selected from thegroup consisting of formaldehyde, glyoxaLand pyruvic aldehyde, from 0.01 to 1.5% by weight of an acid-reacting catalyst, and between and by volume of .a wateremiscible liquid which is substantially'free from any swelling. effect ontextile and .does not react withthe aldehyde under. acid conditions, said water-miscibleliquid being selected from the group consisting .of.1,4-dioxane, acetonyl acetone, diethylone glycol diethyl ether and dimethoxy tetraethylene glycol, the temperature of said medium being maintained substantially constant from the time of, introduction throughout the reaction at a point raised sufliciently to effect reaction between the textile material and the aldehyde but below the boiling pointof the medium under the pres sure prevailing during the reaction.

11. A method as defined in claim 10 in which the textile material is of regenerated cellulose.

References Cited in the file of this patent UNITED STATES PATENTS Number 1 Name Date 2,175,183 Dreyfus 0ct..10,1939 2,240,388 Calva Apr. 29, 1941 2,311,080 I Pinkney Feb. 16, 1943 FOREIGN PATENTS llumber Country Date 460,201 Great Britain Jan. 22, 1937 i OTHER REFERENCES Goldthwait-Textile Research Journal, Jan- ;uary 1951, pages 55 to 61, Reaction of Formaldehyde With Cotton. 

1. A METHOD COMPRISING THE STEP OF INTRODUCING A HYDROPHILIC, WATER-SWELLABLE, WATER-INSOLUBLE CELLULOSIC TEXTILE MATERIAL CONTAINING FREE HYDROCYL GROUPS IN THE MOLECULE INTO A HEATED REACTION MEDIUM WHICH EXERTS A CONTROLLED SWELLING ACTION ON THE TEXTILE AND CONTAINS WATER, BETWEEN 2.5% AND 10% BY WEIGHT OF AN ALDEHYDE SELECTED FROM THE GROUP CONSISTING OF FORMALDEHYDE, GLYOXAL, AND PYRUVIC ALDEHYDE, FROM 0.01 TO 1.5% BY WEIGHT OF AN ACID-REACTING CATALYST, AND BETWEEN 70 AND 95% BY VOLUME OF A WATERMISCIBLE LIQUID WHICH IS FREE FROM ANY SUBSTANTIAL SWELLING EFFECT ON THE TEXTILE AND DOES NOT REACT WITH THE ALDEHYDE UNDER ACID CONDITIONS, SAID WATER-MISCIBLE LIQUID HAVING AN AFFINITY FOR WATER GREATER THAN THAT OF CELLULOSE AND FORMING AN AZEOTROPE WITH WATER BOILING IN THE RANGE OF 80* TO 110* C., THE TEMPERATURE OF SAID MEDIUM BEING MAINTAINED SUBSTANTIALLY CONSTANT FROM THE TIME OF INTRODUCTION THROUGHOUT THE REACTION AT A POINT RAISED SUFFICIENTLY TO EFFECT REACTION BETWEEN THE TEXTILE MATERIAL AND THE ALDEHYDE BUT BELOW THE BOILING POINT OF THE MEDIUM UNDER THE PRESSURE PREVAILING DURING THE REACTION. 